1. Field of the Invention
The present invention relates to a heat exchanging system for a vehicle, which adjusts a cooling performance of a cooling fan by controlling a rotational speed of an electric motor using a semiconductor switching element.
2. Related Art
JP-A-62-251418 proposes an automotive heat exchanging system for adjusting a cooling performance of a cooling fan by using a semiconductor switching element. This conventional system includes a suction-type cooling fan disposed on the vehicle rear side of a radiator which cools an engine cooling water. Air generated by the cooling fan flows from the vehicle front side to the vehicle rear side.
A fan shroud is disposed between the radiator and the cooling fan for guiding cool air to readily pass through the radiator. An electric motor for driving the cooling fan is disposed in a downstream air part of the fan shroud using a plurality of stays. A rotational speed of the electric motor is controlled according to a pulse width modulated control (i.e., PWM control) performed by a control device having a semiconductor switching element. Thus, the rotational speed of the cooling fan is controlled by the control device to control a ventilation performance of the cooling fan.
Further, the control device has a plurality of radiation fins for facilitate heat radiation of the semiconductor switching element. The control device having the radiation fins is attached to a downstream-air-side surface of a stay which is formed wider than the other stays, so that the attachment of the control device to the fan shroud is reinforced.
However, because the control device is attached to the wider stay, a ventilation resistance becomes larger in the wider stay, resulting in deterioration of the ventilation performance of the cooling fan. Even if the stay to which the control device is attached is narrower, the control device protrudes outwardly from the stay and interrupts air flow. Thus, there is a problem that the ventilation performance of the cooling fan is deteriorated.